Art of coloring wood.



UNITED STATES PATENT OFFICE. WILLIAM a. HALL, orfNEw YORK, N. Y ASS IGNOR TO AMERICANMAHOGANY. COMPANY, A v CORPORATION OF MINE:

A OF concerns. woon. Q

Specification of Letters Patenti Patented Oct. 13, 19.08.

i Application filed April 2, 1906. Serial'Nof3095409.

To all whom it may concern:

Be it known that I, WILLIAM A. HALL, a

citizen of the United States, residing at New, York, in the county of New York and State,

some kinds of hard woods, such, for exam-- le, as birch, are much more valuable for umber, for use in building cabinet work, than are the ghter parts of such woods. For example, the red hearts of birch wood command aprice at wholesale for lumber purposes, at from $40.-,-to $50'. or

more per thousand feet, whereas .the light parts of the same wood bring only something like $18.--to $20. per thousand feet, at the same points of delivery. It is 7 therefore very desirable that these lighter parts of thewood be darkened, as this will render them much more valuable for lumber urposes, and I have discovered that by subectmg logs, blocks or other forms of wood to the action of very hot water under pressure for such a length of time as will cook the wood entirely through, the lighter. arts of the wood are so stained by their coo ed resinous and gelatinous ingredients as to render the wcgod permanently much darker, or of a browmsh or reddish color, after it has been dried and converted into lumber.

The invention is carried into effect by placing boards, blocks or logs of Wood in water in closed receptacles or tanks and then heatmg the water to temperatures above 212 degrees Fahrenheit, and preferably to temperatures varying from 290 to 300 degrees ahrenheit, which will be'indicated rom about 65 to 85 pounds of steam pressure to the square inch; the blocks or logs being. subjected to the boiling rocess or the actlon of the hot water until t ey may be said to be thoroughly cooked. The cookin process is kept up for several hours in the c osed tanks .-or receptacles, which-may be of any wellknown construction which will permit of considerable steam pressure, and consequently high temperatures; so that the resinous and gelatinous parts of the wood'willbe thoroughly cooked, and thereby stain the lighter wood to areddish or brownish tinge, these darkened colors being retained by the wood after the same has been driedand conpurposes or forverted into lumber in any suitable manner. The time of cooki will vary with the sizes of the logs or the egree of hardness of.' the wood. For smalllogs or soft wood about -two hours will .be-s'uflicient, but for. larger logs and harder woods the. time of cooking may be increased up .to ten or twelve hours.

While the cooking of the wood at high tem-' peratures, as above indicated, will very considerably darken the same, suchdarkening eflects'may be increased. or varied by adding various .chemicals to the water in:which the wood is cooked. For-example, by adding'a solution ofborax to the Water a reddish tinge will be given to the Wood, this reddishtinge being the. darker the greater the percentage of the borax solution, and while a 2% solution of borax will considerably redden the darkened wood this reddish effect will be increased by increasing the strength of" the borax solution. Also by using a solution of salts of ironin the cooking water greenishgray tints are given to the darkened wood; and these efiects may be varied by varying the strength of the solution of salts of iron, or by using difierent iron salts. A 5% solution of sulfate of iron or a 2% solution of chlorid of iron, will conduce to the greenish-gray :added to the Water to stain or darken the wood. In the latter instance'the wood 1s stained to but a little depth from the surfaces, but the eflect of the chemicals which combine with the cooked ingredients of the wood to produce diflerent shades is to stain or color the wood throughout, or at least down to the heart, according to the time during which the cooking process is continued.

It is found that by cooking the wood for the purpose of darkening the same the wood is also hardened, more or less, when the same isdried and converted into or rendered suitthe cooking water whichis-turned very dark thereby. The removal of a certain percentage of the ligneous matter from the wood would render the same somewhat li hter,

when dried, than it was before being su j ected to the cooking rocess, but where certain salts or solutions of solid matter such, forexample, as the salts of iron hereinbefore referred to, are added to the water in which the cooking is done, such salts not only ofl'set in weight the ligneous matter which has leached out in the cooking process, but also serve to offset or counteract what would otherwise be an injurious destructive effect due to the cooking. of the wood at the high temperatures referred to; the said salts also filling the pores. and making the wood much harder than it otherwise would be, as also deepening the color of the wood further than would be effected by the cooking process in water alone. It has been definitely ascertained that the lumber vthus cooked at. high temperatures in water containing certain salts or solutions of solid matter is much less inclined to war andcrack when dried than when it is cooke in plain water, so that-the wood is not only darkened by the process of cooking the The herein described process of darkening and hardening wood for lumber purposes, consisting in thoroughly cooking boards, logs or blocks of wood for several hours in water to which has been added certain salts or solutions of solid matter which combine with the ingredients of the wood to darken and harden the same, such cooking being effected in a closed receptacle at a temperature or temperatures exceeding 240 F. so as to permanently darken the light parts of the wood by the staining effects resulting from the cooked resinous and gelatinous ingredients thereof augmented by the effects of the chemical salts or solutions added to the cooking Water, the said salts or solutions serving to offset or counteract any destructive effects due to cooking at high temperatures and also counteracting a tendency of the wood to warp and crack when drie In testimony whereof I affix my signature, in presence of two witnesses.

' WILLIAM A. HALL.

Witnesses:

A. W. PERKINS, THEODORE H. FRAEHLICT. 

